Hippocrates of Cos. (circa 460-377 BC). Hippocrates is often referred to as the 'Father of Medicine.' His contribution to medicine includes detailed observations of disease and its effect, and an understanding of how health is often influenced by diet and external influences. This early Greek physician wrote an oath for physicians affirming the profession’s responsibility to fulfill its obligation to adhere to proper conduct in the practice of medicine. At a number of medical schools some variation of this oath is still repeated at graduation.